1. Field of the Invention
This invention relates to new esters of olefinically unsaturated, carboxylic acids containing an ester residue of an hydroxycarboxylic acid-alcohol adduct and polymeric compounds obtained therefrom by homo- or copolymerization. The oil-soluble polymers are excellent flow promoters or crystallization inhibitors for paraffin- and/or wax-containing hydrocarbon mixtures, especially mineral oils. Therefore, the oil-soluble polymers comprise effective pour point depressants, for example, for paraffin-containing crude oils.
2. Description of Related Art
During crude oil shortages, there generally is a steady increase in the production and processing of oils having a relatively high content of high melting point, paraffinic hydrocarbons, i.e., hydrocarbons which are solid at room temperature. Crystallization of the relatively high-melting point constituents causes these oils to lose their fluidity on cooling, e.g., to ambient temperatures. In order to avoid problems during production, transport and processing of these oils, so-called flow or fluidity promoters, also known as crystallization inhibitors and pour point depressants, normally are added to warm crude oil, typically as it accumulates at the well. As long as the oil is warm, the normally solid paraffins remain in solution. The flow promoters, which are generally polymeric materials, prevent the formation of relatively large aggregates of paraffin crystals and, in so doing, improve the crude oil's fluidity. The improved fluidity is evidenced by a reduction in the oil's pour point, i.e., the lowest temperature at which the crude oil is fluid as defined by a standard method, hence the alternative identification of these additives as pour point depressants. These materials also are used for reducing the pour point of diesel oil and lubricating oils.
Several polymeric pour point depressants are known. German Offenlegungsschrift 22 64 328 describes using polymeric acrylates (alcohol esters) containing from 18 to 24 carbon atoms in the alcohol moiety. One disadvantage of these compounds is that high concentrations, e.g., from about 0.01 to 3% by weight, based on the crude oil, must be used to be effective. Another disadvantage is that stock solutions of these flow promoters, usually a 30 to 50 wt.% solution in toluene, are very difficult to handle at temperatures of lower than about 15.degree. C.
Similar disadvantages also are encountered using the polymeric (methy)acrylic acid esters described in German Offenlegungsschrift 32 26 252 (Great Britan 2,125,805A). The long-chain alcohol (C.sub.14 -C.sub.22) residues of these esters have been chain-extended by reaction with ethylene oxide and/or propylene oxide. Even though these products are effective pour point depressants at lower concentrations, stock solutions are virtually impossible to handle at temperatures below about 0.degree. C.
An object of the present invention is to provide new oil-soluble monomers which may be polymerized to homo- and/or copolymers having improved properties as flow promoters. In particular, it is an object of the present invention to provide a pour point depressant which can be handled at a temperature of below about 0.degree. C. as a comparatively concentrated stock solution.